Radio communication apparatus

Abstract

A plurality of carriers are divided into two systems, one on a low-frequency side and the other on a high-frequency side, a transmitting unit that executes processing for transmitting a signal wirelessly is provided in each of the two systems, and output lines of transmit amplifiers of each of the transmitting units are directly coupled and input to an antenna. A feedback unit on the low-frequency side feeds a low-frequency carrier signal portion contained in the transmit signal back to a distortion compensating unit on the low-frequency side, and a feedback unit on the high-frequency side feeds a high-frequency carrier signal portion contained in the transmit signal back to a distortion compensating unit on the high-frequency side. The distortion compensating units compensate for distortion on the low- and high-frequency sides.

1. A radio communication apparatus in which a plurality of carriers are divided into two systems, one on a low-frequency side and the other on a high-frequency side, and which has a transmitting unit in each system that executes processing for transmitting a signal wirelessly, and a distortion compensating unit in each system that compensates for distortion produced in the transmit signal, said apparatus comprising:
 a coupler for directly coupling, and inputting to a single antenna, final stages of respective ones of the transmitting units; and 
 feedback units for feeding a transmit signal, which is input to the antenna, back to respective ones of the compensating units of the two systems; 
 wherein said feedback unit on the low-frequency side feeds a carrier signal portion on the low-frequency side contained in the transmit signal back to said distortion compensating unit on the low-frequency side, and said feedback unit on the high-frequency side feeds a carrier signal portion on the high-frequency side contained in the transmit signal back to said distortion compensating unit on the high-frequency side. 
 
     
     
       2. The apparatus according to  claim 1 , wherein each of said transmitting units on the low- and high-frequency sides includes:
 a combiner for combining a plurality of carrier signals; 
 a quadrature modulator for applying quadrature modulation to the combined signal using a local signal having a frequency of 1.5W 0  or greater, where W 0  represents the frequency bandwidth of the combined signal; and 
 a frequency converter for up-converting the frequency of a signal, which is output from said quadrature modulator, to radio frequency. 
 
     
     
       3. The apparatus according to  claim 2 , wherein if the frequency converter on the low-frequency side has raised the frequency by f 0 , then the frequency converter on the high-frequency side raises the frequency by (f 0 +W 0 ). 
     
     
       4. The apparatus according to  claim 2 , wherein said feedback unit on the low-frequency side includes:
 a frequency converter for down-converting the frequency of the antenna input signal by an amount by which the frequency converter of said transmitting unit on the low-frequency side up-converted the frequency; 
 a digital converter for converting an output of this frequency converter to a digital signal; and 
 a low-pass filter for passing, and inputting to said distortion compensating unit on the low-frequency side, the carrier signal portion on the low-frequency side contained in a signal that is output from this digital converter; and 
 said feedback unit on the high-frequency side includes: 
 a frequency converter for down-converting the frequency of the antenna input signal by an amount by which the frequency converter of said transmitting unit on the high-frequency side up-converted the frequency; 
 a digital converter for converting an output of this frequency converter to a digital signal; and 
 a high-pass filter for passing, and inputting to said distortion compensating unit on the high-frequency side, the carrier signal portion on the high-frequency side contained in a signal that is output from this digital converter. 
 
     
     
       5. The apparatus according to  claim 1 , wherein each of said transmitting units on the low- and high-frequency sides includes:
 a combiner for combining a plurality of carrier signals; 
 a quadrature modulator for applying quadrature modulation to the combined signal, which has undergone distortion compensation by said distortion compensating units, using a local signal having a frequency of 1.5W 0 , where W 0  represents the frequency bandwidth of the combined signal; and 
 a frequency converter for up-converting the frequency of a signal, which is output from said quadrature modulator, to radio frequency; 
 the frequency converter on the low-frequency side raising the frequency by f 0 , and the frequency converter on the high-frequency side raising the frequency by (f 0 +W 0 ). 
 
     
     
       6. The apparatus according to  claim 5 , wherein said feedback unit on the low-frequency side includes:
 a frequency converter for lowering the frequency of an input signal a total of(f 0 −W 0 ); 
 a digital converter for converting an output of said frequency converter to a digital signal; and 
 a low-pass filter for passing the carrier signal portion on the low-frequency side contained in a signal that is output from said digital converter; and 
 a quadrature demodulator for applying quadrature demodulation to an output signal of said low-pass filter using a local signal having a frequency of 2.5W 0 , and inputting the demodulated signal to the distortion compensating unit on the low-frequency side; and 
 said feedback unit on the high-frequency side includes: 
 a frequency converter for lowering the frequency of an input signal a total of f 0 ; 
 a digital converter for converting an output of said frequency converter to a digital signal; and 
 a high-pass filter for passing the carrier signal portion on the high-frequency side contained in a signal that is output from said digital converter; and 
 a quadrature demodulator for applying quadrature demodulation to an output signal of said high-pass filter using a local signal having a frequency of 2.5W 0 , and inputting the demodulated signal to the distortion compensating unit on the high-frequency side. 
 
     
     
       7. The apparatus according to  claim 1 , wherein said feedback unit on the low-frequency side has a low-pass filter and inputs a distorted signal, which has been produced on the low-frequency side, to said distortion compensating unit on the low-frequency side together with a main signal on the low-frequency side, and said feedback unit on the high-frequency side has a high-pass filter and inputs a distorted signal, which has been produced on the high-frequency side, to said distortion compensating unit on the high-frequency side together with a main signal on the high-frequency side. 
     
     
       8. A radio communication apparatus, which has a first system for amplifying a signal for a first transmission band and a second system for amplifying a signal for a second transmission band having a frequency higher than that of the first system, for transmitting a signal of the first transmission band and a second of the second transmission band after amplification of these signals from a common antenna as a transmit signal, the apparatus comprising:
 a first pre-distortion compensating unit for applying pre-distortion compensation processing to a signal that is input to the first system; 
 a second pre-distortion compensating unit for applying pre-distortion compensation processing to a signal that is input to the second system; 
 a low-pass filter provided for a signal that has been obtained by applying a first frequency conversion to a feedback signal obtained by feeding back the transmit signal after amplification thereof, said low-pass filter having a region that passes the signal for the first transmission band and a region that blocks the signal for the second transmission band; and 
 a high-pass filter provided for a signal that has been obtained by applying a second frequency conversion to a feedback signal obtained by feeding back the transmit signal after amplification thereof, said high-pass filter having a region that passes the signal for the second transmission band and a region that blocks the signal for the first transmission band; 
 wherein an output from said low-pass filter is applied to said first pre-distortion compensating unit and an output from said high-pass filter is applied to said second pre-distortion compensating unit.